The recent development of thin semiconductor packages has been accompanied by several problems. For example, in mounting flat packages on printed circuit boards, the packages are dipped in a hot solder bath, which often causes the packages to be cracked by thermal impact if the semiconductors are encapsulated with conventional epoxy resin compositions. It is also recently reported that if semiconductor packages contain moisture prior to mounting on printed circuit boards, hot solder bath dipping can induce steam explosion within the packages, also resulting in cracks.
Attempts for overcoming the crack problem have been made from both the aspects of frame and encapsulating resin, but none of them are successful.